Sister chromatid exchange in aplastic anemia

Role of maternal exposures and newborn genotypes on newborn chromosome aberration frequencies

Maternal exposures may induce chromosome damage and birth defects in the fetus. Polymorphic variation in genes coding for enzymes involved in metabolic activation and detoxification of environmental procarcinogens may account for some of the differences in chromosome aberration frequencies in newborns. In this study, 40 mothers completed questionnaires regarding exposures they received during their pregnancy. Umbilical cord blood samples were analyzed for chromosome aberrations. An average of 1020 metaphase cell equivalents (equal to 1020 G-banded cells) were examined from each newborn. In 26 of the newborns, genotyping analysis was performed for genes functioning in metabolic activation and detoxification (cytochrome P450 genes: CYP2D6 and CYP1A1, and phase II genes: NAT1, NAT2, GSTT1, GSTM1, GSTP1, and epoxide hydrolase). A significant association between the CYP1A1 MspI polymorphism and chromosome aberration frequencies was observed in the newborns (p=0.02), with heterozygotes showing higher aberration frequencies than the wild type homozygotes. Some large differences in chromosome aberration frequencies for other genotypes were also noted, but these were not statistically significant. Exposure to tobacco smoke in utero also appeared to increase translocation frequencies. The mean frequency of translocations per 100 cell equivalents from newborns of mothers who smoked during pregnancy was significantly higher than that of newborns whose mothers did not smoke (0.21 vs. 0.11, respectively, p=0.045).

Analysis of karyotype, SCE, and point mutation of RAS oncogene in Indian MDS patients

Thirty Indian patients diagnosed as having primary myelodysplastic syndrome as per the French-American-British classification were investigated, on admission, for the frequencies of nonrandom karyotype abnormalities, sister chromatid exchange, and point mutations of the RAS oncogene. Successful karyotype analysis was possible in 24 patients, of whom 9 (37.5%) showed nonrandom karyotypic changes. Anomalies of chromosomes 5, 7, and 8 were detected in their bone marrow (BM). In addition, two new anomalies, del(8)(q22) and +19, were observed for the first time in our series. Six MDS patients were studied for SCE in either BM or peripheral blood. These data revealed a normal SCE incidence. Of the 10 MDS patients studied for point mutations of NRAS 12 and 61 and KRAS 12 and 61, one patient exhibited a base substitution at position 1 of the 12th codon of the KRAS gene. These data, gathered for the first time on the Indian patients, throw some light on the nature of genetic changes in MDS of our country.

Frequency of constitutional chromosome alterations in patients with hematologic neoplasias

From 1978 to 1985 cytogenetic studies were performed on 718 patients with different hematologic diseases. Nine (1.25%) had a constitutional chromosome alteration. One patient had trisomy 21, four had balanced translocations and four had sex chromosome anomalies. Although the frequency of constitutional alterations was twice that seen in the newborn population, an analysis of these data and also from the literature shows a random association between constitutional chromosome alterations and hematologic neoplasias, except for patients with Down's syndrome.

Increased sister chromatid exchange frequency in bone marrow cells of myelodysplastic syndromes

The frequency and distribution of sister chromatid exchange (SCE) was determined in bone marrow and peripheral lymphocytes of patients with preleukemic myelodysplastic syndromes. Patients with refractory anemia (RA), RA with excess of blasts (REAB), RA with ring sideroblasts, and RA in transformation presented a 2-3-fold increase in SCE frequency in the bone marrow cells. In contrast, lymphocytes from these patients showed only a marginal increase in SCE. Analysis of interchromosomal distribution of SCE indicated a preferential involvement of chromosomes in group C in patients with RA with excess of blasts. Furthermore, the SCE in patients was not found to be influenced by the karyotype status.

Cytogenetic differentiation of Fanconi anemia, "idiopathic" aplastic anemia, and Fanconi anemia heterozygotes

We have analyzed chromosome breaks in 8 patients with Fanconi anemia (FA), 42 with "idiopathic" aplastic anema (AA), 15 first-degree relatives of FA patients, and 13 controls. Their lymphocytes were treated in culture with three concentrations of mitomycin-C (MMC). A 60-fold increase in breaks was observed in FA patients as compared to AA patients, regardless of severity of clinical signs. The MMC-stress test was standardized to clearly differentiate FA from other pancytopenias in doubtful cases. Also, the effect of storage of MMC in solution was investigated. The data on SCEs of 12 subjects tested, 10 mo apart, showed an inverse relationship between length of storage of MMC and chromosome damage. The 10-month-old solution induced only one half as many SCEs as it induced at 4 months. Further, the usefulness and power of diepoxybutane (DEB) in detection of FA heterozygotes was investigated in 12 first-degree relatives of patients with Fanconi anemia and 12 healthy controls. The mean number of chromosome breaks per mitosis by DEB stress in obligate heterozygotes was 0.08 in comparison to 0.06 in controls. Four of twelve control subjects showed proportions of breaks almost identical to or higher than those of FA heterozygotes, ie, 0.12, 0.10, 0.10, and 0.11 breaks per mitosis. The responses of healthy controls to DEB could be separated into two groups: one with mean chromosome breaks of 0.11 per mitosis, and a second with mean breaks of 0.04 per mitosis. Thus, it appears that heterozygote detection by DEB stress of cultured lymphocytes is not unequivocal.

SCE, X-radiation sensitivity and mutation rate in multiple sclerosis

In order to detect any underlying DNA abnormality that may be present in multiple sclerosis (MS), the incidence of SCE, X-radiation sensitivity and the frequency of 6-thioguanine-resistant cells were determined in the lymphocytes of 34 MS patients. As a group, MS patients showed an increase in the SCE rate compared to control. However, there was no increase in X-radiation sensitivity. The frequency of 6-thioguanine-resistant mutant cells was also normal.

Sister-chromatid exchange (SCE) analysis in mothers exposed to DNA-damaging agents and their newborn infants

The incidence of SCE in the lymphocytes of mothers and their newborn infants was determined. A detailed antenatal history of parental habits such as smoking, alcohol consumption and possible exposure to DNA-damaging agents was documented. The results showed that the SCE rate in the newborn is significantly less than that of their mothers. Mothers who consumed alcohol, but not cigarette smokers, had a significantly increased SCE rate compared to control mothers. However, these maternal habits did not affect the SCE rate of their infants. Neonates with neural tube defects showed a significantly increased SCE rate compared to normal babies.